1. Field of the Invention
The present invention relates to an ultrasonic type flow sensor for use in, for instance measuring a blood flow passing through an auxiliary artificial heart pump which is widely used in a cardiac surgery.
2. Related Art Statements
During a cardiac surgery, an auxialiary heart is widely utilized, and then it is required to monitor a blood flow passing through the auxialiary heart with the aid of a blood flowmeter. Such a blood flowmeter has been described in a Japanese Patent Application Laid-open Publication No. 2005-192687.
In the known ultrasonic type blood flowmeter disclosed in the above mentioned Publication, a flow sensor of the blood flowmeter includes two piezoelectric tranducers serving as an ultrasonic signal transmission and reception element, and a transmission of a signal supplied from an electrical circuit device to each of the piezoelectric tranducers as well as a transmission of a signal supplied from each of the piezoelectric tranducers to the electrical circuit device are performed by means of four lead wires each having one end soldered to the piezoelectric transducer and the other end connected to the electrical circuit device. An operation for soldering the lead wire to the piezoelectric transducer requires a time consuming labor work. Moreover, the piezoelectric transducer is liable to be damaged by heat during the soldering operation, and therefore the soldering should be conducted within a short time period at a predetermined temperature. This requires a substantial skill for the operator. Furthermore, if an excessive tensile force is applied to the lead wires, the piezoelectric transducer might be broken. Therefore, a treatment of the lead wires is rather cumbersome.
Upon the cardiac surgery, the blood flowmeter can be used only once, and after the surgery the used blood flowmeter has to be disposed together with an auxialiary artificial heart in view of infection. Contrary to this, the electrical circuit device is not subjected to the problem of infection and can be used repeatedly. Therefore, the blood flow sensor is detachably connected to the electrical circuit device. Accordingly, the blood flow sensor has to be designed so as to be easily and positively coupled with the electrical circuit device. Moreover, it is sometimes required to reduce a cost of the blood flow sensor itself.